A variable-capacity swash plate compressor used in the air-conditioning system of a motor vehicle or the like is provided with a rotating shaft rotatably driven by the rotational force of the engine, a swash plate linked to the rotating shaft so that the angle of inclination can be varied, a compression piston linked to the swash plate, and the like. In the compressor, the stroke of the piston is varied by varying the angle of inclination of the swash plate to control the discharge rate of the coolant gas.
The angle of inclination of the swash plate can be continuously varied by appropriately controlling the pressure in the control chamber and adjusting the state of balance of the pressure acting on both surfaces of the piston. This is achieved using a capacity control valve opened and closed by electromagnetic force while applying the suction pressure of the suction chamber for drawing in the coolant gas, the discharge pressure of the discharge chamber for discharging the coolant gas pressurized by the piston, and the control chamber pressure of the control chamber (crank chamber) for accommodating the swash plate.
FIG. 5 shows an example of a conventional capacity control valve (refer, for example, to Patent Document 1).
A capacity control valve 100 is constructed of a valve unit and a drive unit for opening and closing the valve unit. The valve unit has a cylindrical valve housing 101, and is formed by arranging a first pressure-sensitive chamber 102, a valve chamber 103, and a second pressure-sensitive chamber 107 in sequence in the axial direction in the interior. The first pressure-sensitive chamber 102 is in communication with a crank chamber via a communication hole 101a formed in the outside peripheral surface of the valve housing 101. The second pressure-sensitive chamber 107 is in communication with a suction chamber via a communication hole 101e formed in the outside peripheral surface of the valve housing 101. The valve chamber 103 is in communication with a discharge chamber via a communication hole 101b formed in the outside peripheral surface of the valve housing 101. The first pressure-sensitive chamber 102 and the valve chamber 103 can be in communication with each other via a valve hole 101c. A support hole 101d is formed between the valve chamber 103 and the second pressure-sensitive chamber 107.
A cylindrical valving element 104 is accommodated in the valve chamber 103. The valving element 104 can slide in the support hole 101d while the outside peripheral surface of the valving element 104 is in close contact with the inside peripheral surface of the support hole 101d, allowing the valving element 104 to move in the axial direction of the valve housing 101. One end of the valving element 104 can open and close the valve hole 101c, and the other end protrudes into the second pressure-sensitive chamber 107.
One end of a rod-shaped linking part 106 is fixed to one end of the valving element 104. The other end of the linking part 106 is disposed so as to be able to contact a bellows 105, and has the function of transmitting the displacement of the bellows 105 to the valving element 104.
The drive unit has a cylindrical solenoid housing 112. The solenoid housing 112 is coaxially linked to the other end of the valve housing 101, and a solenoid 114 is accommodated in the solenoid housing 112.
A control current is supplied to the solenoid 114, whereupon the solenoid 114 generates an electromagnetic force, attracts a moveable core 108 toward a fixed core 110, and acts on the valving element 104 in a closing direction.
The valving element 104 preferably has good operability because the capacity control valve is opened and closed by electromagnetic force and the pressure in the control chamber is appropriately controlled to control the capacity of the compressor while using the suction pressure of the suction chamber, the discharge pressure of the discharge chamber, and the control chamber pressure of the control chamber (crank chamber) of the variable-capacity swash plate compressor. The valving element 104 of a conventional capacity control valve has a structure in which the outside peripheral surface slides while in close contact with the inner peripheral surface of the support hole 101d formed between the second pressure-sensitive chamber 107, which is in communication with the suction chamber via the communication hole 101e of the valve housing 101, and the valve chamber 103, which is in communication with the discharge chamber via the communication hole 101b, as described above. This produces defects such as a hindrance to the movement of the valving element 104 when foreign matter is caught in the sliding parts, or an occasional stoppage of operation. In addition, when the clearance of the sliding parts is increased in order to prevent foreign matter from being caught in this manner, control fluid leaks via the sliding parts, and the designated control function of the compressor is adversely affected.
Ingress from the discharge chamber or the suction chamber can be considered as a pathway for foreign matter to be caught in the sliding parts of the support hole 101d and the valving element 104 of the capacity control valve 100, but the difference between the discharge pressure and the suction pressure suggests that the ingress primarily occurs from the discharge chamber. Assuming, for example, that the aperture dimensions of the meshes in the discharge filter is 160 μm, foreign matter having the same or smaller dimensions will be able to enter the sliding parts. Al, Fe, Si, and the like, which are used in compressor housings, can be cited as the materials constituting the foreign matter.